Method of making heat exchange units



1941- R. M. STIKELEATHER- 2,267,315

METHOD OF MAKING HEAT EXCHANGE UNITS Original Filed Feb. 15, 1939 tubes.

Patented Dec. 23, 1941 Robert M. Stikeleather, Dedham, Mass., assignorto B. F. Sturtevant Company, Boston, Mass.

Original application February 15, 1939, Serial No. 256,475. Divided andthis application July 15.

1940, Serial No. 345,475

2 Claims.

This invention relates to heat exchange tubes and relates moreparticularly to methods and apparatus for anchoring heat exchange tubesin end plates extending transversely of the tubes,

This application is adivision of my copending application Serial No.256,475, filed Feb. 15, 1939.

For the conditioning of air it is convenient to provide heat exchangetubes such, for example, as refrigerant condensers and air coolingrefrigerant evaporators in units including several horizontal rows oftubes, each row containing several tubes. The tubes are usuallyconnected in a series-parallel circuit with respect to interior fluidflow, by return bends at the ends of adjacent tubes. It is also usual toprovide vertically extending end plates at the ends of the tubes, theend plates containing circular openings through which the tubes extend,with the end plates between the ends of the tubes and the return bends.The end plates serve as air tguliding passages and to support and alignthe n es.

Heretofore it has been the practice to either solder or braze the endplates directly to the tubes. Neither practice has proved satisfactory.For duties such as for railroad cars where considerable motion andvibration is present, the

end plates move relative the tubes and loosen the soldered joints. Tobraze the end plates to the tubes requires that the end plate and tubesbe raised to thebrazing temperature. Sucli high temperatures result inthe relatively thin fins adjacent the end walls, always used on thistype of tube, being burned and weakened.

According to this invention tubular bushings are expanded into thecircular openings in the end walls and the outer ends of the bushingsare brazed to the ends of the tubes while simultaneously the ends of thetubes are brazed to the return bends. The end walls and the bushingsprotect the extended-surface fins from the high brazing temperatures.

An object of the invention is to improve the method of securing endAnother objectof the invention is to anchor end plates more securely toheat exchange tubes without damaging the tubes.

Other objects of the invention will be apparent from the drawing and thefollowing description.

The invention will now be described with reference to the drawing, orwhich:

plates to heat exchange exchange tube assembly embodying the invention,and

Fig. 2 is a sectional view along the line 2-2 of Fig. 1.

tinned in the circular apertures with solder.

Tubular copper bushings 8 have portions adapted to fit. into theapertures 6 correspondingly tinned and the bushings are then' placedwithin the apertures and are expanded into the end plate by a suitabletool to take the shape chosen by Fig. l of the drawing. The expandedbushings have recessed portions 9 which fit into the circular aperturesG and have the raised shoulder portions I0 and II on each side of eachrecessed portion 9.

The plate 5 is then placed on the tubes and its position is regulated bythe shoulders ll contacting at their inner edges the outer edges of theinnermost fins [2 which thus space properly the position of the tubeends with respect to the outer ends of the bushings '8. The outer endsl3 of the tubes are then flared as illustrated by Fig. 1 with the outerends of the bushings 8 so as to tightly contact same. The return bend I4is then placed in position as shown by Fig. 1,withits two ends withinthe flared portions l3 of the tubes.

After the above described assembly operations have taken place, heat isapplied. to the outer portions of the bushings 8 and the flared portionsll of the tubes, brazing compound is flowed in between the bushings 8and the flared portions l3 of the tubes and between the ends of thereturn bend and the flared portions l3, and the bushings are brazed tothe flared portions of the tubes and the flared portions of the tubesare brazed to the ends of the return bend. Sumcient heat is alsotransmitted through the bush- I Fig. l is a side elevation insection ofa heat should be understood that the invention is not limited to theexact apparatus and arrangements of apparatus shown as modifications maysuggest themselves to those skilled in the art without said return.bend.

ing said bushing to said tube and said tube to 15 2. The method oi?attaching an end plate to a -,tube which comprisesaperturing the plate,tinning the periphery ofthe aperture with solder, tinning anintermediate exterior portion 01' a 5 tubular bushing with solder,placing the tinned portion of the bushing within the aperture, expandingthe bushing into the aperture, placing the plate over the tube with theouter end of the bushing around one end of the tube, and

10 brazing the bushing to the tube while simultaneously through. theconduction of heat through the bushing, sweatingthe tinned areas of thebushing and the plate together.v

, ROBERT M. STIKELEA'I'HER.

